Anti-splay head and set screw for spinal fixation

ABSTRACT

An anti-splaying system having a base, first and second arms, first and second locking channels. Each of the first and second locking channels is formed in a respective one of the arms, from a proximal opening to a proximal bottom at or adjacent a proximal beginning of an inner thread in the arm. The system can instead or also include a set screw having a driving portion, a body portion, external threads extending from the body portion, and an intermediate locking component connected rotatably to the body portion. The intermediate locking component and the channels are configured such that the locking component can, in operation of the system, be moved into a securing position in the locking channels and, when in the secured position, fixes the two arms from splaying away from each other. The technology also includes methods for making the system or components thereof.

FIELD

The present technology is related generally to spinal fixation systemsand processes and, more particularly, to an anti-splay head andset-screw arrangement.

BACKGROUND

Surgical screws and rods are used commonly in surgically correctingspinal abnormalities. Pedicle screw assemblies are used to facilitateplacement and attachment of a spinal rod relative to the spine. Suchpedicle screw assemblies include at least a bone screw section or anchorand at least one receiver portion attached to the bone screw. The bonescrew sections are anchored to the vertebrae in the surgical procedure.

The receiver portions have arms between which portions of the spinal rodis received. The arms are often configured with internal threadingcorresponding to threading on a set screw. Following screw anchoring inthe bone, and placement of the rod between the arms of the receiver, aset screw is threaded between the arms to secure the rod in thereceiver.

The receiver portions of typical pedicle screws can be angularly orfixedly positionable with respect to the screw sections to facilitateddesired attachment of the spinal rod between vertebrae.

Outward forces on the receiver arms over time following implantation tryto splay the arms away from each other. One manner of limiting splay isby receiver and set-screw threads configured, such as with slopingthread faces, such that the set screw holds the arms inward, against theset screw.

Other attempted solutions for splaying include using a cap installablearound at least a portion an exterior of the receiver arms, to hold thearms from moving away from each other.

These and other prior efforts to avoid splaying have variousshortcomings. Shortcomings include undesirable cost, form factor (e.g.,implant size or fit within the patient), and strength over time.

SUMMARY

The systems, process, and techniques of this disclosure relate generallyto an anti-splay head and set-screw arrangement.

In one aspect, the present disclosure provides an anti-splaying system.The system includes a receiver having a base, a first arm, a second arm,a first locking channel, and a second locking channel. The first arm andthe second arm each extend from the base defining a rod-receiving cavitybetween the arms. The first and second arms include first and secondinner threads formed in respective inner surfaces of the first andsecond arms. The first locking channel is formed in the inner surface ofthe first arm and extending from a proximal opening to a proximal bottomat or adjacent a first proximal beginning of the first inner thread. Thesecond locking channel is formed in the inner surface of the second armand extending from a proximal opening to a proximal bottom at oradjacent a second proximal beginning of the second inner thread.

Further in this aspect, the system includes a set screw having a drivingportion, a body portion, external threads extending from the bodyportion, and an intermediate locking component connected rotatably tothe body portion.

The intermediate locking component of the set screw and the lockingchannels of the receiver are configured such that the locking componentcan, in operation of the system, be moved into a securing position inthe locking channels and, when in the secured position, fixes the twoarms from splaying away from each other.

The intermediate locking component is connected rotatably to the bodyportion intermediate the driving portion and the external threads of theset screw.

The locking component comprises opposing lateral ends sized and shapedcorresponding to size and shape of the locking channel, for matingengagement between the locking component and the locking channels.

A first lateral end of the lateral ends comprises opposing shoulderssized and shaped to engage opposing shoulders of a first locking channelof the locking channels

The lateral ends include first and second lateral ends, and theconnecting component includes first and second arms connecting the firstand second lateral ends respectively to the ring.

The locking channel has a depth that is about twice as deep as thelocking ends are tall or less.

The locking component includes a ring surrounding a portion of the setscrew body. The body has a reduced diameter where the ring surrounds thebody.

In another aspect, the system further includes a bone anchor connectablewith the receiver, and the spinal rod.

In still another aspect, the technology includes methods of making anyof the anti-splaying systems or anti-splay components described above.

Details of one or more aspects of the disclosure are set forth in theaccompanying drawings and the description below. Other features,objects, and advantages of the techniques described in this disclosurewill be apparent from the description, drawings, and claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows perspective views of an anti-splaying system partiallydisassembled, the system including an anti-splay receiver and ananti-splay set screw, according to embodiments of the presentdisclosure;

FIG. 2 is a cross section of the anti-splay set screw taken along lineF2-F2 of FIG. 1;

FIG. 3 is a side view of the anti-splaying system of FIG. 1;

FIG. 4 is a perspective view of the anti-splay set screw being loweredfor insertion to the receiver;

FIG. 5 is the perspective view of FIG. 4 with the anti-splay set screwbeing threaded toward a final position within the anti-splay receiver;

FIG. 6 is a bottom view of the anti-splay set screw;

FIG. 7 is a top view of the anti-splay receiver;

FIG. 8 is the top view of FIG. 7, with the anti-splay set screw insertedinto the anti-splay receiver; and

FIG. 9 is a cross section of the anti-splaying system, assembled, takenalong line F9-F9 of FIG. 1.

DETAILED DESCRIPTION

Turning now to the drawings, and more particularly to the first figure,FIG. 1 shows a perspective view of components of an anti-splay system,indicated generally by reference numeral 100.

The system 100 includes an anti-splay head, or receiver 110, and ananti-splay set screw 120, according to embodiments of the presentdisclosure.

The receiver 110 has arms 112 extending up, or proximally, from a base113. The arms 112 define a rod cavity 114 between them, for receiving aspinal-fusion rod. A rod 300 is shown schematically, disposed in thecavity 114, in FIGS. 3 and 8.

The set screw 120 extends from a driving, or proximal, end having adriving portion 122. The driving portion 122 includes a driving port123. The driving port 123 may be a cavity sized and shaped correspondingto any available set-screw driver (now shown).

The set screw 120 further includes a shaft, or body 125 extending to adistal end of the screw 120. In a contemplated embodiment, the drivingportion 122 can be formed integrally or monolithically with or in thebody 125 of the set screw 120.

The body 125 has a threaded exterior 126. The threaded surface 126corresponds in size and shape to a thread 116 of the receiver 110, forbeing threaded into the receiver.

The set screw 120 further includes a locking component 124. The lockingcomponent 124 is connected rotatably to the body 125, as indicated byarrows in FIG. 1.

The locking component 124 is in various embodiments connected to thebody 125 intermediate the driving portion 122 and the screw threads 126.The locking component 124 can be referred to in such cases as anintermediate locking component, an intra-screw locking component, or thelike.

While the arrows in FIG. 1 indicate a first direction of rotation, theconnecting features are in various embodiments configured so that thelocking component 124 can rotate in both direction, or in one directionor the other, only.

The locking component 124 extends between opposing ends 128. The ends128 of the locking component 124 are connected by a central connector130. The connector in various embodiments is shaped as a ring 130. Thering 130 surrounds a portion of the body 125 extending up to the drivingportion 122, as shown well in FIG. 2. In various embodiments, the body125 has a reduced diameter to accommodate the ring, as shown in FIG. 2.

The connection in various embodiments includes features facilitating therelative rotation between the ring 130 and the body 125, such asball-bearings or a medical lubricant.

The ends 128 can extend by arms 127 connecting the ends 128 to thecentral connecting structure 130, e.g., connecting ring 130.

With further reference to the anti-splay receiver 110, each arm 112 hasan internal thread set 116. As shown in FIG. 1, each thread set 116 isinterrupted or separated by an anti-splay, or locking, channel 118 at aproximal end of the receiver threads 116. The threads 116 oppose eachother across the cavity 114, and can be referred to as opposing threadsor thread sections.

Each locking channel 118 extends distally from a proximal opening 117(referenced in FIG. 1) to a distal stop or bottom. In operation of thesystem 100, the anti-splay set screw 120 is threaded into the anti-splayreceiver 110 until the locking component 124 enters the locking channel118. The threading can be performed until the locking component 124engages with the channel stop 119 (FIG. 7) and/or the distal end of thebody engages the spinal rod 300 (FIGS. 3 and 8). Engaging the rod is inmost embodiments the priority.

The locking channel 118 is sized and shaped, and the anti-splay setscrew 120 is sized and shaped, such that the set screw 120 extendsdistally in being threaded into the receiver 110 until the rod iscontacted by the distal end of the rod. At that time, or after a certainsmall amount of further threading, such as a quarter, half, or full turnof the screw 120, the locking component 124 bottoms out at stop 119 ofthe channel 118. The system 100 is in some embodiments designed, and therod sized, such that the locking end 128 enters the channel 118completely, even if it doesn't bottom out.

The locking channel must be sufficiently deep. If the locking channel118 is not deep enough, the locking component 124 would bottom out, atthe stop 119, before the set screw 120 is able to thread sufficientlyinto the receiver 110.

In various embodiments, the stop 119 is at or adjacent a top of thecorresponding inner thread 116. The stop 119 may be at or adjacent afirst, second, or third level of inner threading 116, for instance. Inthe example of FIG. 1, the channel extends through a single level ofinner thread from the top or opening 117, with the stop 119 beinggenerally at start of a second level of inner thread from the top oropening 117. These areas, including the first one or few threads, can bereferred to generally as a proximal beginning of the inner thread.

In various embodiments, the channel depth is at least equal to a heightof the locking component 124, or a height of the ends 128 of the lockingcomponent 124.

In contemplated embodiments, the system 100, or a kit in which thesystem is provided, includes any of the components referenced. Thesystem or kit can include any suitable components for performing thesurgical procedures, including but not limited to implantable componentsand instruments for effecting the surgery. The system 100 can include,for instance, any of the anti-splay receiver 110, the anti-splay setscrew 120, and the rod 300. The system 100 or kit can include the driverreferenced, but not shown. And the system 100 or kit can include anynumber and size of these parts, including multiple anti-splay set screwsand receivers 120, 110.

Turning to the second figure, FIG. 2 illustrates a cross section of theset screw 120, taken along line F2-F2 of FIG. 1.

In operation of the system 100 (FIG. 1), the locking component 124 isaligned into the locking channel 118 of the receiver 110, by a surgeonor surgical robot. As the anti-splay set screw 120 is threaded into thereceiver 110, by the surgeon or robot turning a driver (or, drivinginstrument; not shown) against a driving portion 220 of the drivingportion 122, the locking component 124 enters the channel 118.

FIG. 3 is a side view of the anti-splay receiver 110 and anti-splay setscrew 120 of FIG. 1. Rotatability of the locking component 124 relativeto the set-screw body 125 is indicated again by arrow.

FIG. 3 also shows schematically an end view of the rod 300 positioned inthe cavity 114 of the receiver 110.

FIG. 4 is a perspective view of the anti-splay set screw 120 beingpositioned for lowering for insertion to the anti-splay receiver 110.The movement is indicated generally by arrow in FIG. 4.

Prior to the movement of FIG. 4, the receiver 110 is secured to apatient vertebra, by a bone screw connected to the receiver 110. Thebone screw (not shown) can be any conventional or available type. Thereceiver 110 can be configured for top-loading or bottom-loading of thebone screw into the receiver 110. The receiver 110 may in such ways beconnected or connectable to the bone anchor readily—e.g., easily in theusual course of a surgery.

The anti-splay receiver 110 and anti-splay bone screw 120 can be furtherconfigured to allow desired relative motion, such as uniaxial ormultiaxial motion. In some embodiments, the bone screw and the receiver110 are fixed together, either by being formed integrally ormonolithically, or by being fixedly connected to each other.

In operation of the anti-splaying system 100, before and/or as theset-screw 120 is moved toward the receiver 110, care is taken such thatthe locking ends 128 of the locking component 124 are aligned with theanti-splay channels 118 of the arms 112 of the receiver 110.

The anti-splay channels 118 receive ends 128 of the locking component124. In various embodiments the locking component 124 is sized such thatthe ends extend further laterally than a maximum diameter of the screwbody 125, and in some cases farther than a maximum diameter than thethread 126, as shown in the figures, and best seen in FIG. 2.

FIG. 5 shows the anti-splay set screw 120 having been threaded to afinal position within the anti-splay receiver 110. In this position, thelocking component 124 would seat against the rod 300, which is shown inFIGS. 3 and 8. Motion of threading, transitioning the set screw 120toward the final position, is indicated by arrow in FIG. 5.

FIG. 6 is a bottom view of the anti-splay set screw 120. Relativerotatability between the set screw body 125 and the locking component124 is indicated by arrow in FIG. 6, as in FIG. 1.

The ends 128 of the locking component 124 are configured such that, whenengaged with the arms 112 of the receiver 110, being slid into theanti-splay channels 118, keep the arms 112 from moving away from eachother. The connection keeps each arm 112 from moving away from the otherarm—i.e., keeps the arms 118 from splaying.

The ends 128 of the locking component 124 include first engagement orlocking features 600, such as shoulders. The shoulders 600, which may bereferred to as external shoulders, engage second, corresponding,engagement or locking features 700 (FIG. 7) of the receiver 110. Theshoulders 600 of the locking component 124 can be referred to asexternal shoulders, corresponding to internal shoulders 800 of thereceiver 110.

The configuration of each end 128 can be referred to as adouble-dovetail, corresponding to the opposing shoulders 600.

In contemplated embodiments (not shown in detail), the locking orengaging features are configured in any of a variety of other ways. Thefeatures may include the locking component 124 having at each end 128opposing internal shoulders. In this case, the internal shoulders of thelocking component 124 form a locking-component void, for engaging withopposing external shoulders of a protrusion extending from or on aninner surface of each arm 112 of the receiver 110, for instance. In thiscase, the locking component 124 is aligned so that the protrusion of thereceiver 112 is received in the void of the locking component 124, asthe internal shoulder of the locking component 124 is slid down alongthe external shoulder of the protrusion of the receiver arms 112.

FIG. 7 illustrates a plan view of the anti-splay receiver 110. The viewshows a top-down, or proximately looking, view of the receiver includinganti-splay channels 118.

FIG. 8 is the top view of FIG. 7, with the anti-splay set screw 120inserted into the anti-splay receiver 110, yielding the anti-splayingsystem 100 assembled. Full assembly in some embodiments includes theanti-splay set screw and receiver 120, 110 being connected to the boneanchor (not shown).

The rod 300 is shown seated in the anti-splay receiver 110. The rod 300is secured in place there by the receiver 110 and the anti-splay setscrew 120 threaded to the receiver 110, with the ends 128 of the lockingcomponent 124 secured in the anti-splay channel 118 of the receiver 110.

It should be understood that various aspects disclosed herein may becombined in combinations other than the combinations presentedspecifically in the description and the accompanying drawings. It shouldalso be understood that, depending on the example, certain acts orevents of any of the processes or methods described herein may beperformed in other sequence, added, merged, or left out altogether(e.g., all described acts or events may not be necessary to carry outthe techniques).

Any disclosure or claim herein referencing direction is not meant tolimit interpretation of the disclosure, unless the disclosure or claimrequires expressly such limitation. Reference, for instance, to movementup or down herein is not limited to movement in any certain directionduring surgery or system assembly, as the surgery or assembly can beperformed with any of a wide variety or orientations or in any suitablereference frame.

In addition, while certain aspects of this disclosure are described asbeing performed by a single module or unit for purposes of clarity, itshould be understood that the techniques of this disclosure may beperformed by a combination of units or modules associated with, forexample, a medical device.

Unless defined specifically otherwise herein, all terms are to be giventheir broadest possible interpretation including meanings implied fromthe specification as well as meanings understood by those skilled in theart and/or as defined in dictionaries, treatises, etc. It must also benoted that, as used in the specification and the appended claims, thesingular forms “a,” “an,” and “the” include plural referents unlessotherwise specified, and that the terms “comprises” and/ or“comprising,” when used in this specification, specify the presence ofstated features, elements, and/or components, but do not preclude thepresence or addition of one or more other features, steps, operations,elements, components, and/or groups thereof.

It will be understood that various modifications may be made to theembodiments disclosed herein. Therefore, the above description shouldnot be construed as limiting, but merely as exemplification of thevarious embodiments. Those skilled in the art will envision othermodifications within the scope and spirit of the claims appended hereto.

1-20. (canceled)
 21. An anti-splaying system comprising: a spinalconstruct comprising spaced apart first and second arms, inner surfacesof the arms defining an implant cavity, the spinal construct comprisinga first channel extending into the inner surface of the first arm and asecond channel extending into the inner surface of the second arm, thespinal construct comprising a first opening extending into a proximalsurface of the first arm and the inner surface of the first arm and asecond opening extending into a proximal surface of the second arm andthe inner surface of the second arm; and a coupling member having a bodyand a ring coupled to the body, the coupling member comprising spacedapart first and second projections each extending outwardly from thering, the projections each being configured to be inserted through oneof the openings and into one of the channels to diminish the arms fromsplaying away from each other.
 22. The anti-splaying system recited inclaim 21, wherein the ring is rotatably coupled to the body, theopposing ends of the projections each engage portions of one of the armswhen the projections are disposed in the channels.
 23. The anti-splayingsystem recited in claim 21, wherein opposing ends of each of theprojections each define a first locking feature and opposing portions ofeach of the arms that define portions of one of the channels each definea second locking feature, the second locking features of each of thearms engaging the first locking features of one of the projections whenthe projections are disposed in the channels.
 24. The anti-splayingsystem recited in claim 21, wherein opposing ends of each of theprojections each define a first shoulder and opposing portions of eachof the arms that define a portion of one of the channels each define asecond shoulder, the second shoulders of each of the arms engaging thefirst shoulders of one of the projections when the projections aredisposed in the channels.
 25. The anti-splaying system recited in claim21, wherein the first and second projections each include opposing firstand second ends that each engage portions of one of the arms that defineopposing first and second ends of one of the channels when theprojections are disposed in the channels.
 26. The anti-splaying systemrecited in claim 25, wherein first and second ends of each of theprojections define a double-dovetail configuration.
 27. Theanti-splaying system recited in claim 25, wherein portions of each ofthe arms have a configuration that corresponds to the double-dovetailconfiguration of the projections.
 28. The anti-splaying system recitedin claim 21, wherein the coupling member includes a male thread formconfigured for engagement with female thread forms that extend into theinner surfaces of the arms.
 30. The anti-splaying system recited inclaim 28, wherein the channels each extend through a portion of one ofthe female thread forms.
 31. The anti-splaying system recited in claim28, wherein the channels are each in communication with one of thefemale thread forms.
 32. The anti-splaying system recited in claim 28,wherein threads of the female thread forms each define a distal portionof one of the channels.
 33. The anti-splaying system recited in claim28, wherein the ring is positioned between a proximal portion of thebody and a proximal portion of the male thread form to prevent axialtranslation of the ring relative to the body.
 34. The anti-splayingsystem recited in claim 21, wherein the body has a reduced diameterwhere the ring surrounds the body.
 35. An anti-splaying systemcomprising: a spinal rod; a spinal construct comprising spaced apartfirst and second arms defining an implant cavity therebetween configuredfor disposal of the spinal rod, the spinal construct comprising a firstchannel extending into an inner surface of the first arm and a secondchannel extending into an inner surface of the second arm, the spinalconstruct comprising a first opening extending into a proximal surfaceof the first arm and the inner surface of the first arm and a secondopening extending into a proximal surface of the second arm and theinner surface of the second arm; and a coupling member having a body anda ring rotatably coupled to the body, the coupling member comprisingspaced apart first and second projections each extending outwardly fromthe ring, the projections each being configured to be inserted throughone of the openings and disposed in one of the channels to diminish thearms from moving away from each other.
 36. The anti-splaying systemrecited in claim 21, wherein the implant cavity is U-shaped andcorresponds to a shape of the spinal rod.
 37. The anti-splaying systemrecited in claim 21, wherein the first and second projections eachinclude opposing first and second ends that each engage portions of oneof the arms that define opposing first and second ends of the channelswhen the projections are disposed in the channels.
 38. The anti-splayingsystem recited in claim 37, wherein first and second ends of each of theprojections define a double-dovetail configuration.
 39. Theanti-splaying system recited in claim 37, wherein first and second endsof each of the portions of the arms each have a configuration thatcorresponds to the double-dovetail configuration of the projections. 40.An anti-splaying system comprising: a spinal construct comprising spacedapart first and second arms defining an implant cavity therebetween, thespinal construct comprising a first channel extending into an innersurface of the first arm and a second channel extending into an innersurface of the second arm, the spinal construct comprising a firstopening extending into a proximal surface of the first arm and the innersurface of the first arm and a second opening extending into a proximalsurface of the second arm and the inner surface of the second arm; and acoupling member having a body and a ring, the ring rotatably coupled tothe body, the body having a reduced diameter where the ring surroundsthe body, the coupling member comprising spaced apart first and secondprojections each extending outwardly from the ring, the projections eachbeing configured to be inserted through one of the openings and disposedin one of the channels, wherein the first and second projections eachinclude opposing first and second ends that each engage portions of oneof the arms that define opposing first and second ends of the channelswhen the projections are disposed in the channels, wherein first andsecond ends of each of the projections define a double-dovetailconfiguration, and wherein first and second ends of each of the portionsof the arms each have configuration that corresponds to thedouble-dovetail configuration of the projections.